If just few hundred/thousand is enough to start a civil war, then there would been lot of civil wars eveerywhere esp in west asia. Why couldn't kurds start a civil war in iraq/turkey/iran??? Even in vietnam, if North vietnam hadn't got support from former USSR, china, they couldn't have so succesful. Even in a'stan if west had not supplied money/weapons to mujahideens, ussr could not have failed in such a manner. Even in desh, if not for constant support from pakis, JnK would not have seen so huge terrorism problem.
To sustain a civil war, they need money/arms support. If MB can self-finance themselves like taliban is currently doing, then maybe yes. Taliban is getting around 400 million$ annually. Wahabbis see MB as a rival islamic group. Saudis are fine with MB to an extent, but if they felt MB went too independent, they will certainly act against MB.
WRT suez canal if egypt army cannot maintain an open suez canal, then considering its importance, i suppose an international force will come and sit there to have an open and free canal.